1. Field of the Invention
The presently disclosed subject matter relates to a lens device and, in particular, a technology of adjusting falling of a lens in a barrel.
2. Description of the Related Art
In a lens device of a broadcasting television camera, a variable power lens (an extender lens) is inserted as required along an imaging optical path of an imaging lens system (an optical system), thereby changing the magnifying power of an image. For example, with a 2× extender lens, by operating an operation lever or the like provided outside to place the extender lens in the imaging path, an image can be imaged as being magnified twofold.
As depicted in FIG. 6, an extender lens 100 is disposed between a front master group and a rear master group. The extender lens 100 includes a front optical system (lens group) and a rear optical system (lens group). The optical performance (optical characteristics) of the extender lens 100 can be adjusted by adjusting a space between the front lens group and the rear lens group along an optical axis direction. The space adjustment described above is performed by screwing a lens frame 101 holding the front lens group and a lens frame 102 holding the rear lens group together with a screw and rotating a gear wheel 103 formed on the outer perimeter of the lens frame 102 holding the rear lens group by using a jig or the like from outside.
However, this adjustment of the optical characteristics is performed after the extender lens is once removed from the optical axis. On the other hand, the results of adjustment of the optical characteristics are checked with the extender lens being on the optical axis. For this reason, to elaborate the optical characteristics, it is required to repeat the state in which the extender lens is inserted in the optical axis and the state in which the extender lens is removed from the optical axis, which poses a problem in which it takes some time and trouble.
Therefore, a technology capable of adjusting optical characteristics with the extender lens inserted in the optical axis has been desired. As a technology capable of adjusting the optical characteristics described above with the extender lens inserted in the optical axis, inventions are disclosed in Japanese Patent Application Laid-Open No. 2000-075182 and Japanese Patent Application Laid-Open No. 11-249216.
Japanese Patent Application Laid-Open No. 2000-075182 discloses an extender lens with a collar decentered with respect to a shaft center of a spindle being inserted into the spindle for inserting and removing the extender lens along and from an imaging optical path, the color inserted through a hole formed on a case body. For this extender lens, eccentricity can be adjusted by rotating the collar from outside of the case.
Japanese Patent Application Laid-Open No. 11-249216 describes that a gear is formed over an entire peripheral surface of a lens frame and, by rotating a rotating member engaged with this gear and exposed outside of a case, a lens is rotated about an optical axis to adjust eccentricity.